Exchange biased self-pinned spin valve sensor with recessed overlaid leads

ABSTRACT

A spin valve sensor includes an antiparallel (AP) pinned layer structure which is self-pinned without the assistance of an antiferromagnetic (AFM) pinning layer. A free layer of the spin valve sensor has first and second wing portions which extend laterally beyond a track width of the spin valve sensor and are exchange coupled to first and second AFM pinning layers. Magnetic moments of the wing portions of the free layer are pinned parallel to the ABS and parallel to major planes of the layers of the sensor for magnetically stabilizing the central portion of the free layer which is located within the track width. The spin valve sensor has a central portion that extends between the first and second AFM layers. First and second lead layers overlay the first and second AFM layers and further overlay first and second portions of the central portion so that a distance between the first and second lead layers defines a track width that is less than a distance between the first and second AFM layers. The spin valve sensor has a cap layer structure that has a full thickness portion which is located between first and second reduced thickness portions and the first and second lead layers engage the cap layer structure within the first and second reduced thickness portions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exchange biased self-pinned spinvalve sensor with recessed overlaid leads and, more particularly, tosuch a sensor wherein first and second leads engage first and secondrecessed portions of a cap layer of the sensor so that resistancebetween the leads and the sensor is reduced.

2. Description of the Related Art

The heart of a computer is a magnetic disk drive which includes arotating magnetic disk, a slider that has write and read heads, asuspension arm and an actuator arm. When the disk is not rotating theactuator arm locates the suspension arm so that the slider is parked ona ramp. When the disk rotates and the slider is positioned by theactuator arm and suspension arm above the disk, air is swirled by therotating disk adjacent an air bearing surface (ABS) of the slidercausing the slider to ride on an air bearing a slight distance from thesurface of the rotating disk. When the slider rides on the air bearingthe actuator arm swings the suspension arm to place the write and readheads over selected circular tracks on the rotating disk where fieldsignals are written and read by the write and read heads. The write andread heads are connected to processing circuitry that operates accordingto a computer program to implement the writing and reading functions.

An exemplary high performance read head employs a spin valve sensor forsensing the magnetic field signals from the rotating magnetic disk. Thesensor includes a nonmagnetic electrically conductive first spacer layersandwiched between a ferromagnetic pinned layer structure and aferromagnetic free layer structure. An antiferromagnetic pinning layertypically interfaces the pinned layer structure for pinning a magneticmoment of the pinned layer structure 90° to the air bearing surface(ABS) wherein the ABS is an exposed surface of the sensor that faces themagnetic disk. First and second leads are connected to the spin valvesensor for conducting a sense current therethrough. A magnetic moment ofthe free layer structure is free to rotate upwardly and downwardly withrespect to the ABS from a quiescent or bias point position in responseto positive and negative magnetic field signals from the rotatingmagnetic disk. The quiescent position, which is preferably parallel tothe ABS, is the position of the magnetic moment of the free layerstructure with the sense current conducted through the sensor in theabsence of field signals.

The thickness of the spacer layer is chosen so that shunting of thesense current and a magnetic coupling between the free and pinned layerstructures are minimized. This thickness is typically less than the meanfree path of electrons conducted through the sensor. With thisarrangement, a portion of the conduction electrons are scattered at theinterfaces of the spacer layer with the pinned and free layerstructures. When the magnetic moments of the pinned and free layerstructures are parallel with respect to one another scattering isminimal and when their magnetic moments are antiparallel scattering ismaximized. Changes in scattering changes the resistance of the spinvalve sensor as a function of cos θ, where θ is the angle between themagnetic moments of the pinned and free layer structures. Thesensitivity of the sensor is quantified as magnetoresistive coefficientdr/R where dr is the change in the resistance of the sensor as themagnetic moment of the free layer structure rotates from a positionparallel with respect to the magnetic moment of the pinned layerstructure to an antiparallel position with respect thereto and R is theresistance of the sensor when the magnetic moments are parallel.

In addition to the spin valve sensor the read head includesnonconductive nonmagnetic first and second read gap layers andferromagnetic first and second shield layers. The spin valve sensor islocated between the first and second read gap layers and the first andsecond read gap layers are located between the first and second shieldlayers. In the construction of the read head the first shield layer isformed first followed by formation of the first read gap layer, the spinvalve sensor, the second read gap layer and the second shield layer.Spin valve sensors are classified as a bottom spin valve sensor or a topspin valve sensor depending upon whether the pinned layer is locatednear the bottom of the sensor close to the first read gap layer or nearthe top of the sensor close to the second read gap layer. Spin valvesensors are further classified as simple pinned or antiparallel (AP)pinned depending upon whether the pinned layer structure is one or moreferromagnetic layers with a unidirectional magnetic moment or a pair offerromagnetic AP layers that are separated by a coupling layer withmagnetic moments of the ferromagnetic AP layers being antiparallel toone another. Spin valve sensors are still further classified as singleor dual wherein a single spin valve sensor employs only one pinned layerand a dual spin valve sensor employs two pinned layers with the freelayer structure located therebetween.

As stated hereinabove, a magnetic moment of the aforementioned pinnedlayer structure is pinned 90° to the ABS by the aforementionedantiferromagnetic (AFM) pinning layer. After deposition of the sensorlayers the sensor is subjected to a temperature at or near a blockingtemperature of the material of the pinning layer in the presence of afield which is oriented perpendicular to the ABS for the purpose ofresetting the orientation of the magnetic spins of the pinning layer.The elevated temperature frees the magnetic spins of the pinning layerso that they align perpendicular to the ABS. This also aligns themagnetic moment of the pinned layer structure perpendicular to the ABS.When the read head is cooled to room temperature the magnetic spins ofthe pinning layer are fixed in the direction perpendicular to the ABSwhich pins the magnetic moment of the pinned layer structureperpendicular to the ABS. After resetting the pinning layer it isimportant that subsequent elevated temperatures and extraneous magneticfields do not disturb the setting of the pinning layer. It is alsodesirable that the pinning layer be as thin as possible since it islocated within the track width of the sensor and its thickness adds toan overall gap length between the first and second shield layers. Itshould be understood that the thinner the gap length the higher thelinear read bit density of the read head. This means that more bits canbe read per inch along the track of a rotating magnetic disk whichenables an increase in the storage capacity of the magnetic disk drive.

A scheme for minimizing the aforementioned gap between the first andsecond shield layers is to provide a self-pinned AP pinned layerstructure. The self-pinned AP pinned layer structure eliminates the needfor the aforementioned pinning layer which permits the read gap to bereduced by 120 Å when the pinning layer is platinum manganese (PtMn). Inthe self-pinned AP pinned layer structure each AP pinned layer has anintrinsic uniaxial anisotropy field and a magnetostriction uniaxialanisotropy field. The intrinisic uniaxial anisotropy field is due to theintrinsic magnetization of the layer and the magneto striction uniaxialanisotropy field is a product of the magneto striction of the layer andstress within the layer. A positive magnetostriction of the layer andcompressive stress therein results in a magnetostriction uniaxialanisotropy field that can support an intrinsic uniaxial anisotropyfield. The orientations of the magnetic moments of the AP pinned layersare set by an external field. This is accomplished without theaforementioned elevated temperature which is required to free themagnetic spins of the pinning layer.

If the self-pinning of the AP pinned layer structure is not sufficient,unwanted extraneous fields can disturb the orientations of the magneticmoments of the AP pinned layers or, in a worst situation, could reversetheir directions. Accordingly, there is a strong-felt need to maximizethe uniaxial magnetostriction anisotropy field while maintaining a highmagnetoresistive coefficient dr/R of the spin valve sensor.

It is also important that the free layer be longitudinally biasedparallel to the ABS and parallel to the major planes of the thin filmlayers of the sensor in order to magnetically stabilize the free layer.This is typically accomplished by first and second hard bias magneticlayers which abut first and second side surfaces of the spin valvesensor. End portions of the free layer abutting the hard bias layers areover-biased and become very stiff in their response to field signalsfrom the rotating magnetic disk. The stiffened end portions can take upa large portion of the total width of a sub-micron sensor and cansignificantly reduce the amplitude of the sensor. It should also beunderstood that a narrow track width is important for promoting thetrack width density of the read head. The more narrow the track widththe greater the number of tracks that can be read per linear inch alonga radius of the rotating magnetic disk. This enables a further increasein the magnetic storage capacity of the disk drive.

There is a need to reduce the total stack height of the read sensorwithout sacrificing the magnetoresistive coefficient dr/R. There is alsoa need to reduce the stiffening of the magnetic moment of the free layerwhen longitudinally biased and to minimize disturbance of the magneticmoments of the AP pinned layers.

SUMMARY OF THE INVENTION

An aspect of the invention is to employ an exchange biasing scheme forlongitudinally biasing the free layer. This is accomplished by providingthe free layer with first and second wing portions which extendlaterally beyond the track width of the sensor and which interface firstand second antiferromagnetic (AFM) biasing layer layers so as toimplement an exchange bias therebetween. This arrangement will enhancethe stabilization of the free layer and will result in the read headhaving a higher amplitude read output.

The spin valve sensor has a central portion which extends between thefirst and second AFM layers. An aspect of the invention is to providefirst and second lead layers which overlay the first and second AFMlayers respectively and further overlay first and second portionsrespectively of the central portion of the spin valve sensor so that adistance between the first and second lead layers defines a track widthof the sensor that is less than a distance between the first and secondAFM layers. With this arrangement uniform biasing of the free layer ispromoted.

A spin valve sensor further includes a cap layer structure whichtypically includes a layer of tantalum (Ta). Another aspect of theinvention is to provide the cap layer structure with a full thicknessportion which is located between first and second reduced thicknessportions with the first and second lead layers engaging the cap layerstructure within the first and second reduced thickness portions. Sincetantalum (Ta) has a high resistance the reduced thickness portionsprovide less resistance between the first and second lead layers and thesensor for conducting the sense current therethrough.

A further aspect of the invention is to provide a self-pinningantiparallel (AP) pinned layer structure without an AFM pinning layerpinning the AP pinned layer structure. The self-pinning is accomplishedby providing the ferromagnetic AP pinned layers within the AP pinnedlayer structure with uniaxial anisotropies which are orientedperpendicular to the ABS and, in combination, self-pin the magneticmoments of the first and second AP pinned layers perpendicular to theABS and antiparallel with respect to each other. Cobalt iron (CoFe) ispreferably employed for each of the first and second AP pinned layers ina self-pinned AP pinned layer structure.

An object of the present invention is to provide a low stack height spinvalve sensor with an exchange biased free layer, a self-pinnedantiparallel (AP) pinned layer structure which has a highmagnetoresistive coefficient dr/R, a uniformly biased free layer and anarrow track width.

Another object is to provide the aforementioned spin valve sensorwherein first and second lead layers engage first and second reducedthickness portions of a cap layer structure for reducing the resistancebetween the lead layers and the spin valve sensor.

A further object is to provide various methods of making the foregoingread heads.

Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an exemplary prior art magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2—2 of FIG. 1;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the magnetic head taken along plane 5—5 of FIG.2;

FIG. 6 is a partial view of the slider and a merged magnetic head asseen in plane 66 of FIG. 2;

FIG. 7 is a partial ABS view of the slider taken along plane 7—7 of FIG.6 to show the read and write elements of the merged magnetic head;

FIG. 8 is a view taken along plane 8—8 of FIG. 6 with all material abovethe coil layer and leads removed;

FIG. 9 is an enlarged isometric ABS illustration of the read head with aprior art spin valve sensor;

FIG. 10 is an ABS view of one embodiment of the present spin valvesensor; and

FIG. 11 is an ABS view of another embodiment of the present spin valvesensor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, FIGS. 1-3 illustratea magnetic disk drive 30. The drive 30 includes a spindle 32 thatsupports and rotates a magnetic disk 34. The spindle 32 is rotated by aspindle motor 36 that is controlled by a motor controller 38. A slider42 has a combined read and write magnetic head 40 and is supported by asuspension 44 and actuator arm 46 that is rotatably positioned by anactuator 47. A plurality of disks, sliders and suspensions may beemployed in a large capacity direct access storage device (DASD) asshown in FIG. 3. The suspension 44 and actuator arm 46 are moved by theactuator 47 to position the slider 42 so that the magnetic head 40 is ina transducing relationship with a surface of the magnetic disk 34. Whenthe disk 34 is rotated by the spindle motor 36 the slider is supportedon a thin (typically, 0.01 μm) cushion of air (air bearing) between thesurface of the disk 34 and the air bearing surface (ABS) 48. Themagnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of the disk 34, as well as forreading information therefrom. Processing circuitry 50 exchangessignals, representing such information, with the head 40, providesspindle motor drive signals for rotating the magnetic disk 34, andprovides control signals to the actuator for moving the slider tovarious tracks. In FIG. 4 the slider 42 is shown mounted to a suspension44. The components described hereinabove may be mounted on a frame 54 ofa housing 55, as shown in FIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

FIG. 6 is a side cross-sectional elevation view of a merged magnetichead 40, which includes a write head portion 70 and a read head portion72, the read head portion employing a spin valve sensor 74 of thepresent invention. FIG. 7 is an ABS view of FIG. 6. The spin valvesensor 74 is sandwiched between nonmagnetic electrically insulativefirst and second read gap layers 76 and 78, and the read gap layers aresandwiched between ferromagnetic first and second shield layers 80 and82. In response to external magnetic fields, the resistance of the spinvalve sensor 74 changes. A sense current I_(S) conducted through thesensor causes these resistance changes to be manifested as potentialchanges. These potential changes are then processed as readback signalsby the processing circuitry 50 shown in FIG. 3.

The write head portion 70 of the magnetic head 40 includes a coil layer84 which is sandwiched between first and second insulation layers 86 and88. A third insulation layer 90 may be employed for planarizing the headto eliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are sandwiched betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. Since the second shield layer 82 and thefirst pole piece layer 92 are a common layer this head is known as amerged head. In a piggyback head (not shown) the layers 82 and 92 areseparate layers and are separated by an insulation layer. As shown inFIGS. 2 and 4, first and second solder connections 104 and 106 connectleads from the spin valve sensor 74 to leads 112 and 114 on thesuspension 44, and third and fourth solder connections 116 and 118connect leads 120 and 122 from the coil 84 (see FIG. 8) to leads 124 and126 on the suspension.

FIG. 9 is an isometric ABS illustration of the read head 40 shown inFIG. 7. The read head 40 includes the spin valve sensor 74. First andsecond hard bias and lead layers 134 and 136 are connected to first andsecond side surfaces 138 and 139 of the spin valve sensor. Thisconnection is known in the art as a contiguous junction and is fullydescribed in commonly assigned U.S. Pat. No. 5,018,037. The first hardbias and lead layers 134 include a first hard bias layer 140 and a firstlead layer 142 and the second hard bias and lead layers 136 include asecond hard bias layer 144 and a second lead layer 146. The hard biaslayers 140 and 144 cause magnetic fields to extend longitudinallythrough the spin valve sensor 74 for stabilizing a free layer in thesensor. The spin valve sensor 74 and the first and second hard bias andlead layers 134 and 136 are located between the nonmagnetic electricallyinsulative first and second read gap layers 76 and 78 and the first andsecond read gap layers 76 and 78 are, in turn, located between theferromagnetic first and second shield layers 80 and 82.

Unfortunately, the first and second hard bias layers 140 and 144 in FIG.9 do not uniformly stabilize the free layer within the sensor 74. Hardbias layers typically stiffen the magnetic moment of the free layer atthe end portions of the sensor which abut the hard bias layers so thatthese portions are stiff in their response to field signals from therotating magnetic disk. With submicron track widths, the loss inamplitude at each end of the sensor is unacceptable. Further, as theflux lines from the hard bias layers extend between the side surfaces138 and 139, a central portion of the free layer may not be properlystabilized since magnetic flux is progressively drawn in by the firstand second shield layers 80 and 82.

The Invention

One embodiment of the present spin valve sensor 200 is illustrated inFIG. 10 wherein the spin valve sensor is located between the first andsecond read gap layers 76 and 78. The spin valve sensor 200 includes afree layer structure 202 and an antiparallel (AP) pinned layer structure204. A nonmagnetic electrically nonconductive spacer layer (S) 206 islocated between the free layer structure 202 and the AP pinned layerstructure 204. Since the free layer structure 202 is located between theAP pinned layer structure 204 and the second read gap layer 78 and thefirst pole piece layer 92 the spin valve sensor 200 is a bottom spinvalve sensor. A seed layer structure 208 may be located between thefirst read gap layer 76 and the AP pinned layer structure 204. The seedlayer structure 208 may include first, second, third and fourth seedlayers (SL1), (SL2), (SL3) and (SL4) 210, 212, 214 and 216. These seedlayers, with the thicknesses and materials shown, have been found topromote a desirable texture of the layers deposited thereon. A cap layerstructure 218 is located on top of the free layer structure 202 forprotecting the free layer structure from subsequent processing steps.

It should be noted that the spin valve sensor does not include thetypical antiferromagnetic (AFM) pining layer for pining magnetic momentsof the AP pinned layer structure 204. An aspect of the invention is toprovide an AP pinned layer structure 204 which is self-pinning. The APpinned layer structure 204 includes ferromagnetic first and second APpinned layers (AP1) and (AP2) 220 and 222. A nonmagnetic electricallyconductive antiparallel coupling (APC) layer 224 is located between andinterfaces the first and second AP pinned layers 220 and 222. The firstAP pinned layer 220 has a magnetic moment 226 which is orientedperpendicular to the ABS in a direction, either toward the ABS or awayfrom the ABS, as shown in FIG. 10, and the second AP pinned layer has amagnetic moment 228 which is oriented antiparallel to the magneticmoment 226 by a strong antiparallel coupling between the first andsecond AP pinned layers 220 and 222. The preferred material for thefirst and second AP pinned layers 220 and 222 is cobalt iron (CoFe).

In a preferred embodiment, one of the AP pinned layers is thicker thanthe other, such as the first AP pinned layer 220 may be 13 Å and thesecond AP pinned layer 222 may be 20 Å. With this arrangement, themagnetic moment 228 of the second AP pinned layer becomes dominant anddetermines the directions of the magnetic moments 226 and 228. Thedirection of the magnetic moment 228, either into or out of the sensor,is determined by the direction in which the magnetic moment 228 is setby an external magnetic field. With the arrangement shown in FIG. 10,the magnetic field has been applied out of the sensor which causes themagnetic moment 228 to be directed out of the sensor. If the externalfield is reversed in its direction, the magnetic moment 228 would bedirected into the sensor. Alternatively, the first AP pinned layer 220may be thicker than the second AP pinned layer 222. When the AP pinnedlayers 220 and 222 are formed by sputter deposition they are preferablydeposited in the presence of a field which is oriented perpendicular tothe ABS. In this manner, the easy axes of the first and second AP pinnedlayers will likewise be oriented perpendicular to the ABS.

The free layer structure 202 may include first and second free layers(F1) and (F2) 230 and 232. It has been found that when the free layerstructure 202 has a cobalt iron first free layer 230 between the spacerlayer 206 and a nickel iron second free layer 232 that themagnetoresistive coefficient dR/R of the spin valve sensor is increased.The free layer structure has a magnetic moment 234 which is orientedparallel to the ABS and parallel to the major thin film planes of thelayers. A sense current I_(S) is conducted through the spin valve sensorfrom right to left or from left to right, as shown in FIG. 10. When afield signal from the rotating magnetic disk rotates the magnetic moment234 into the sensor the magnetic moments 234 and 228 become moreantiparallel which increases the resistance of the sensor to the sensecurrent I_(S) and when a field signal rotates the magnetic moment 234out of the sensor the magnetic moments 234 and 228 become more parallelwhich decreases the resistance of the sensor to the sense current I_(S).These resistance changes change potentials within the processingcircuitry 50 in FIG. 3 which are processed as playback signals. The caplayer structure 218 may include first and second cap layers 236 and 238wherein the first cap layer is copper and the second cap layer istantalum. The copper layer 236 has been found to provide a betterinterface between the nickel iron second free layer 232 and the tantalumcap layer 238.

The read head has an electrical track width (TW) which is defined by adistance between first and second lead layers (L1) and (L2) 240 and 242which will be discussed in more detail hereinbelow. The free layerstructure 202 has first and second wing portions 244 and 246 whichextend laterally beyond the track width. First and secondantiferromagnetic (AFM) pinning layers 248 and 250 are exchange coupledto the first and second wing portions 244 and 246 so as to pin, byexchange coupling with the wing portions, magnetic moments 252 and 254of the wing portions parallel to the ABS and parallel to the major thinfilm planes of the layers. The magnetic moments 252 and 254, in turn,align and stabilize the magnetic moment 234 of a central portion of thefree layer structure located within the track width (TW). In a preferredembodiment, the free layer structure 202 includes additional free layerportions (F3) 256 and 258 wherein the additional free layer portion 256is located between the wing portion 244 and the AFM layer 248 and theadditional free layer portion 258 is located between the wing portion246 and the AFM layer 250. In a preferred embodiment, each of the AFMlayers 248 and 250 is platinum manganese (PtMn). After completion of thehead, the head may be heated to or near the blocking temperature ofplatinum manganese, which is about 350° C., in the presence of a fieldoriented parallel to the ABS and parallel to the major thin film planesof the layers. This will set the magnetic moments 252 and 254 of thewing portions, as shown in FIG. 10. Each of the layers 210, 212, 214,216, 220, 224, 222 and 206 may extend beyond the track width and havewing portions below the wing portions 244 and 246 of the free layerstructure.

It should be noted that without an AFM pinning layer for the AP pinnedlayer structure 204 that the setting of the magnetic spins of the AFMlayers 248 and 250 will not cause a disturbance of the operation of theAP pinned layer structure. This then enables the use of a singlematerial for the AFM layers 248 and 250. The present invention enablesthe use of platinum manganese (PtMn) as the single AFM pinning materialemployed in the read head.

As shown in FIG. 10, the spin valve sensor has a central portion 260that extends between the first and second AFM layers 248 and 250. Anaspect of the invention is that the first and second lead layers 240 and242 overlay the first and second AFM layers respectively and furtheroverlay first and second portions 262 and 264 respectively of thecentral portion so that a distance between the first and second leadlayers defines a track width (TW) that is less than the distance betweenthe first and second AFM layers 248 and 250. Another aspect of theinvention is that the cap layer structure 218 has a full thicknessportion which is located between first and second reduced thicknessportions, which reduced thickness portions may be the aforementionedfirst and second portions 262 and 264. The first and second lead layers240 and 242 engage the cap layer structure within the first and secondreduced thickness portions 262 and 264. Since the top cap layer istypically tantalum (Ta), which has a high resistance, the reducedthickness portions 262 and 264 lessen the high resistance between thefirst and second lead layers 240 and 242 and the read sensor forconducting the sense current I_(S) therethrough.

Exemplary thicknesses and materials of the layers are 30 Å of Al₂O₃ forlayer 210, 30 Å of NiMnO for the layer 212, 25 Å of NiFeCr for the layer214, 30 Å of PtMn for the layer 216, 13 Å of CoFe for the layer 220, 8 Åof Ru for the layer 224, 20 Å of CoFe for the layer 222, 20 Å of Cu forthe layer 206, 15 Å of CoFe for the layer 230, 15 Å of NiFe for thelayer 232, 6 Å of Cu for the layer 236, 40 Å of Ta for the layer 238, 10Å of NiFe for the layers 256 and 258, and 120 Å of PtMn for the layers248 and 250.

FIG. 11 is another embodiment of the present invention which is a topspin valve 300. The spin valve 300 is located between the first andsecond read gap layers 76 and 78. The spin valve sensor 300 includes afree layer structure 302 and an AP pinned layer structure 304. Anonmagnetic electrically conductive spacer layer (S) 306 is locatedbetween the free layer structure 302 and the AP pinned layer structure304. A seed layer structure 307 is located between the free layerstructure 302 and the first read gap layer 76 and may include first andsecond seed layers (SL1) and (SL2) 308 and 310. With the first seedlayer being nickel manganese oxide and the second seed layer beingtantalum, the texture of the layers deposited thereon has been found tobe improved. A cap layer 312 is located on the pinned layer structure304 for protecting it from subsequent processing steps. Again, the trackwidth of the read head is defined by the distance between first andsecond lead layers (L1) and (L2) 314 and 316 which will be described inmore detail hereinbelow. The pinned layer structure 304 hasferromagnetic first and second AP pinned layers (AP1) and (AP2) 318 and320. A nonmagnetic electrically conductive antiparallel coupling layer(APC) 322 is located between the AP pinned layers 318 and 320. The APpinned layers 318 and 320 have magnetic moments 324 and 326 which areself-pinned in the same manner as described for the AP pinned layerstructure 204 in FIG. 10.

The free layer structure has first and second free layers (F1) and (F2)328 and 329. The free layer structure 302 further has first and secondwing portions 330 and 332 which extend laterally beyond the track width(TW) and are exchange coupled to first and second AFM layers 334 and336. The free layer structure may be provided with additional freelayers (F3) 338 and 340 beyond the track width for improving thestrength of magnetic moments 342 and 344 of the wing portions 330 and332. Again, the magnetic moments 342 and 344 align and stabilize themagnetic moment 346 of the central portion of the free layer structurewithin the track width. If desired, the first and second seed layers 308and 310 may extend laterally beyond the track width and provide supportfor the wing portions 330 and 332 of the free layer structure. Theoperation and setting of the top spin valve sensor in FIG. 11 is thesame as that described for the bottom spin valve sensor in FIG. 10.

In the same manner as the spin valve sensor 200 in FIG. 10 the spinvalve sensor 300 in FIG. 11 has a central portion 350 which extendsbetween the first and second AFM layers 334 and 336. The first andsecond lead layers 314 and 316 overlay the first and second AFM layers334 and 336 respectively and further overlay first and second portions352 and 354 respectively of the central portion so that a distancebetween the first and second lead layers 314 and 316 defines a trackwidth (TW) that is less than a distance between the first and second AFMlayers. A further aspect of the invention is that the cap layer 312 hasa full thickness portion which is located between first and secondreduced thickness portions which may coincide with the aforementionedfirst and second portions 352 and 354. The first and second lead layers314 and 316 engage the cap layer 312 within the first and second reducedthickness portions 352 and 354. As stated hereinabove, when the caplayer 312 is tantalum (Ta) this is a high resistance material betweenthe lead layers and the spin valve sensor. With the arrangement justdescribed, the reduced thickness portions 352 and 354 of the cap layer312 reduce the resistance between the first and second lead layers 314and 316 and the spin valve sensor for conducting the sense current I_(S)therethrough.

Exemplary thicknesses of materials of the spin valve sensor shown inFIG. 11 are 30 Å of NiMnO for the first seed layer 308, 30 Å of Ta forthe second seed layer 310, 15 Å of NiFe for the layer 328, 15 Å of CoFefor the layer 329, 20 Å of Cu for the layer 306, 20 Å of CoFe for thelayer 318, 8 Å of Ru for the layer 322, 13 Å of CoFe for the layer 320,40 Å of Ta for the layer 312, 10 Å of NiFe for the layers 338 and 340,and 120 Å of PtMn for the layers 334 and 336.

Discussion

It has been found that by removing the pinning layer for pinning amagnetic moment of the AP pinned layer that the amplitude read output ofthe read head can be increased 40%. Further, by uniformly stabilizingthe free layer structure and employing the lead overlay scheme theamplitude is still further increased and the track width of the readhead can be made more narrow to increase the read bit density of theread head. It should also be noted that by omitting an AFM pinning layerfor the AP pinned layer structure in each of the embodiments in FIGS. 10and 11 that the stack height of the sensor is significantly less. Withan AFM pinning layer the stack height would be increased about 120 Å.The lower stack height promotes a more narrow gap between the first andsecond shield layers 80 and 82 in FIGS. 6 and 7 which enables the readhead to read more bits per linear inch along a linear track of arotating magnetic disk. It should be understood that the slidersupporting the magnetoresistive sensor may have a head surface otherthan the aforementioned ABS such as a tape surface for use in a tapedrive. Further, the inventive concepts are applicable tomagnetoresistive sensors other than spin valve sensors such as ananisotropic magnetoresistive (AMR) sensor.

A method for constructing the reduced thickness portions 262 and 264 inFIG. 10 and the reduced thickness portions 352 and 354 in FIG. 11 is toform a bilayer resist layer on only the full thickness portion of thecap layer structure and then ion mill, such as reactive ion etching(RIE), into the cap layer so as to reduce its thickness at each end.While the photoresist layer is still in place the first and second leadlayers may then be sputter deposited so that they are located in thereduced thickness portions of the cap layer structure and cover thefirst and second AFM layers. The bilayer resist can then be removed by adissolution process.

The following commonly assigned U.S. patents are incorporated in theirentirety by reference herein: (1) U.S. Pat. No. 5,465,185; (2) U.S. Pat.No. 5,583,725; (3) U.S. Pat. No. 5,768,069; (4) U.S. Pat. No. 6,040,961;(5) U.S. Pat. No. 6,117,569; (6) U.S. Pat. No. 6,127,053; and (7) U.S.Pat. No. 6,219,211 B1.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A magnetic head assembly that has a head surface for facinga magnetic medium, comprising: a read head that includes amagnetoresistive sensor; the magnetoresistive sensor including: anantiparallel (AP) pinned layer structure; a ferromagnetic free layerhaving a magnetic moment that is free to rotate in response to a fieldsignal; and a nonmagnetic electrically conductive spacer layer locatedbetween the free layer and the AP pinned layer structure; theantiparallel (AP) pinned layer structure including: ferromagnetic firstand second antiparallel (AP) pinned layers; an antiparallel (AP)coupling layer located between and interfacing the first and second APpinned layers; and the first and second AP pinned layers self pinningone another without assistance of a pinning layer; the free layer havingfirst and second wing portions that extend in first and second lateraldirections beyond a track width of the sensor; first and secondantiferromagnetic (AFM) layers exchange coupled to said first and secondwing portions for longitudinally biasing the magnetic moment of the freelayer parallel to the head surface and parallel to major planes of thelayers of the read head; the magnetoresistive sensor having a centralportion that extends between said first and second AFM layers; and firstand second lead layers overlaying the first and second AFM layersrespectively and further overlaying first and second portionsrespectively of said central portion so that a distance between thefirst and second lead layers defines a track width that is less than adistance between the first and second AFM layers.
 2. A magnetic headassembly as claimed in claim 1 including: nonmagnetic electricallynonconductive first and second read gap layers; the spin valve sensorbeing located between the first and second read gap layers;ferromagnetic first and second shield layers; and the first and secondread gap layers being located between the first and second shieldlayers.
 3. A magnetic head assembly as claimed in claim 2 furthercomprising: a write head including: ferromagnetic first and second polepiece layers that have a yoke portion located between a pole tip portionand a back gap portion; a nonmagnetic write gap layer located betweenthe pole tip portions of the first and second pole piece layers; aninsulation stack with at least one coil layer embedded therein locatedbetween the yoke portions of the first and second pole piece layers; andthe first and second pole piece layers being connected at their back gapportions.
 4. A magnetic head assembly as claimed in claim 3 wherein thefree layer is located between the AP pinned layer structure and thefirst pole piece layer.
 5. A magnetic head assembly as claimed in claim3 wherein the AP pinned layer structure is located between the freelayer and the first pole piece layer.
 6. A magnetic head assembly thathas a head surface for facing a magnetic medium, comprising: a read headthat includes a magnetoresistive sensor; the magnetoresistive sensorincluding: an antiparallel (AP) pinned layer structure; a ferromagneticfree layer having a magnetic moment that is free to rotate in responseto a field signal; and a nonmagnetic electrically conductive spacerlayer located between the free layer and the AP pinned layer structure;the antiparallel (AP) pinned layer structure including: ferromagneticfirst and second antiparallel (AP) pinned layers; an antiparallel (AP)coupling layer located between and interfacing the first and second APpinned layers; and the first and second AP pinned layers self pinningone another without assistance of a pinning layer; the free layer havingfirst and second wing portions that extend in first and second lateraldirections beyond a track width of the sensor; first and secondantiferromagnetic (AFM) layers exchange coupled to said first and secondwing portions for longitudinally biasing the magnetic moment of the freelayer parallel to the head surface and parallel to major planes of thelayers of the read head; the magnetoresistive sensor having a centralportion that extends between said first and second AFM layers; first andsecond lead layers overlaying the first and second AFM layersrespectively and further overlaying first and second portionsrespectively of said central portion so that a distance between thefirst and second lead layers defines a track width that is less than adistance between the first and second AFM layers; a cap layer structurethat has a full thickness portion and first and second reduced thicknessportions with the full thickness portion located between the first andsecond reduced thickness portions; and said first and second lead layersengaging the cap layer structure within said first and second reducedthickness portions.
 7. A magnetic head assembly that has a head surfacefor facing a magnetic medium, comprising: a read head that includes:nonmagnetic electrically nonconductive first and second read gap layers;a magnetoresistive sensor being located between the first and secondread gap layers; ferromagnetic first and second shield layers; and thefirst and second read gap layers being located between the first andsecond shield layers; the magnetoresistive sensor including: anantiparallel (AP) pinned layer structure; a ferromagnetic free layerhaving a magnetic moment that is free to rotate in response to a fieldsignal; and a nonmagnetic electrically conductive spacer layer locatedbetween the free layer and the AP pinned layer structure; theantiparallel (AP) pinned layer structure including: ferromagnetic firstand second antiparallel (AP) pinned layers; an antiparallel (AP)coupling layer located between and interfacing the first and second APpinned layers; and the first and second AP pinned layers self pinningone another without assistance of a pinning layer; the free layer havingfirst and second wing portions that extend in first and second lateraldirections beyond a track width of the sensor; first and secondantiferromagnetic (AFM) layers exchange coupled to said first and secondwing portions for longitudinally biasing the magnetic moment of the freelayer parallel to the head surface and parallel to major planes of thelayers of the read head; the magnetoresistive sensor having a centralportion that extends between said first and second AFM layers; first andsecond lead layers overlaying the first and second AFM layersrespectively and further overlaying first and second portionsrespectively of said central portion so that a distance between thefirst and second lead layers defines a track width that is less than adistance between the first and second AFM layers; a cap layer structurethat has a full thickness portion which is located between first andsecond reduced thickness portions; said first and second lead layersengaging the cap layer structure within said first and second reducedthickness portions; a write head including: ferromagnetic first andsecond pole piece layers that have a yoke portion located between a poletip portion and a back gap portion; a nonmagnetic write gap layerlocated between the pole tip portions of the first and second pole piecelayers; an insulation stack with at least one coil layer embeddedtherein located between the yoke portions of the first and second polepiece layers; and the first and second pole piece layers being connectedat their back gap portions.
 8. A magnetic disk drive including at leastone magnetic head assembly that has a head surface for facing a magneticmedium and that includes a write head and a read head, comprising: thewrite head including: ferromagnetic first and second pole piece layersthat have a yoke portion located between a pole tip portion and a backgap portion; a nonmagnetic write gap layer located between the pole tipportions of the first and second pole piece layers; an insulation stackwith at least one coil layer embedded therein located between the yokeportions of the first and second pole piece layers; and the first andsecond pole piece layers being connected at their back gap portions; andthe read head including: nonmagnetic electrically nonconductive firstand second read gap layers; a magnetoresistive sensor located betweenthe first and second read gap layers; ferromagnetic first and secondshield layers; and the first and second read gap layers being locatedbetween the first and second shield layers; the magnetoresistive sensorincluding: an antiparallel (AP) pinned layer structure; a ferromagneticfree layer having a magnetic moment that is free to rotate in responseto a field signal; and a nonmagnetic electrically conductive spacerlayer located between the free layer and the AP pinned layer structure;the antiparallel (AP) pinned layer structure including: ferromagneticfirst and second antiparallel (AP) pinned layers; an antiparallel (AP)coupling layer located between and interfacing the first and second APpinned layers; the first and second AP pinned layers self pinning oneanother without assistance of a pinning layer; the free layer havingfirst and second wing portions that extend in first and second lateraldirections beyond a track width of the sensor; first and secondantiferromagnetic (AFM) layers exchange coupled to said first and secondwing portions for longitudinally biasing the magnetic moment of the freelayer parallel to the head surface and parallel to major planes of thelayers of the read head; the spin valve sensor having a central portionthat extends between said first and second AFM layers; and first andsecond lead layers overlaying the first and second AFM layersrespectively and further overlaying first and second portionsrespectively of said central portion so that a distance between thefirst and second lead layers defines a track width that is less than adistance between the first and second AFM layers; a housing; themagnetic medium being supported in the housing; a support mounted in thehousing for supporting the magnetic head assembly with said head surfacefacing the magnetic medium so that the magnetic head assembly is in atransducing relationship with the magnetic medium; a motor for movingthe magnetic medium; and a processor connected to the magnetic headassembly and to the motor for exchanging signals with the magnetic headassembly and for controlling movement of the magnetic medium.
 9. Amagnetic disk drive as claimed in claim 8 wherein the free layer islocated between the AP pinned layer structure and the first pole piecelayer.
 10. A magnetic disk drive as claimed in claim 8 wherein the APpinned layer structure is located between the free layer and the firstpole piece layer.
 11. A magnetic disk drive including at least onemagnetic head assembly that has a head surface for facing a magneticmedium and that includes a write head and a read head, comprising: thewrite head including: ferromagnetic first and second pole piece layersthat have a yoke portion located between a pole tip portion and a backgap portion; a nonmagnetic write gap layer located between the pole tipportions of the first and second pole piece layers; an insulation stackwith at least one coil layer embedded therein located between the yokeportions of the first and second pole piece layers; and the first andsecond pole piece layers being connected at their back gap portions; andthe read head including: nonmagnetic electrically nonconductive firstand second read gap layers; a magnetoresistive sensor located betweenthe first and second read gap layers; ferromagnetic first and secondshield layers; and the first and second read gap layers being locatedbetween the first and second shield layers; the magnetoresistive sensorincluding: an antiparallel (AP) pinned layer structure; a ferromagneticfree layer having a magnetic moment that is free to rotate in responseto a field signal; and a nonmagnetic electrically conductive spacerlayer located between the free layer and the AP pinned layer structure;the antiparallel (AP) pinned layer structure including: ferromagneticfirst and second antiparallel (AP) pinned layers; an antiparallel (AP)coupling layer located between and interfacing the first and second APpinned layers; the first and second AP pinned layers self pinning oneanother without assistance of a pinning layer; the free layer havingfirst and second wing portions that extend in first and second lateraldirections beyond a track width of the sensor; first and secondantiferromagnetic (AFM) layers exchange coupled to said first and secondwing portions for longitudinally biasing the magnetic moment of the freelayer parallel to the head surface and parallel to major planes of thelayers of the read head; the spin valve sensor having a central portionthat extends between said first and second AFM layers; and first andsecond lead layers overlaying the first and second AFM layersrespectively and further overlaying first and second portionsrespectively of said central portion so that a distance between thefirst and second lead layers defines a track width that is less than adistance between the first and second AFM layers; a cap layer structurethat has a full thickness portion and first and second reduced thicknessportions with the full thickness portion located between the first andsecond reduced thickness portions; and said first and second lead layersengaging the cap layer structure within said first and second reducedthickness portions; a housing; the magnetic medium being supported inthe housing; a support mounted in the housing for supporting themagnetic head assembly with said head surface facing the magnetic mediumso that the magnetic head assembly is in a transducing relationship withthe magnetic medium; a motor for moving the magnetic medium; and aprocessor connected to the magnetic head assembly and to the motor forexchanging signals with the magnetic head assembly and for controllingmovement of the magnetic medium.
 12. A method of making a magnetic headassembly which has a head surface for facing a magnetic medium,comprising the steps of: forming a read head that includes amagnetoresistive sensor; a making of the magnetoresistive sensorincluding the steps of: forming an antiparallel (AP) pinned layerstructure; forming a ferromagnetic free layer with a magnetic momentthat is free to rotate in response to a field signal; and forming anonmagnetic electrically conductive spacer layer between the free layerand the AP pinned layer structure; the forming of the antiparallel (AP)pinned layer structure including the steps of: forming ferromagneticfirst and second antiparallel (AP) pinned layers; forming anantiparallel (AP) coupling layer between and interfacing the first andsecond AP pinned layers; and the first and second AP pinned layers beingfurther formed to self pin one another without assistance of a pinninglayer; the free layer being further formed with first and second wingportions that extend in first and second lateral directions beyond atrack width of the sensor; forming first and second antiferromagnetic(AFM) layers exchange coupled to said first and second wing portions forlongitudinally biasing the magnetic moment of the free layer parallel tothe head surface and parallel to major planes of the read head; andforming the magnetoresistive sensor with a central portion that extendsbetween said first and second AFM layers; and forming first and secondlead layers overlaying the first and second AFM layers respectively andfurther overlaying first and second portions respectively of saidcentral portion so that a distance between the first and second leadlayers defines a track width that is less than a distance between thefirst and second AFM layers.
 13. A magnetic head assembly as claimed inclaim 12 including the steps of: forming nonmagnetic electricallynonconductive first and second read gap layers with the spin valvesensor located therebetween; and forming ferromagnetic first and secondshield layers with the first and second read gap layers locatedtherebetween.
 14. A method of making a magnetic head assembly as claimedin claim 13 further comprising the steps of: making a write headincluding the steps of: forming ferromagnetic first and second polepiece layers in pole tip, yoke and back gap regions wherein the yokeregion is located between the pole tip and back gap regions; forming anonmagnetic electrically nonconductive write gap layer between the firstand second pole piece layers in the pole tip region; forming aninsulation stack with at least one coil layer embedded therein betweenthe first and second pole piece layers in the yoke region; andconnecting the first and second pole piece layers at said back gapregion.
 15. A method as claimed in claim 14 wherein the free layer isformed between the AP pinned layer structure and the first pole piecelayer.
 16. A method as claimed in claim wherein 14 the AP pinned layerstructure is located between the free layer and the first pole piecelayer.
 17. A method of making a magnetic head assembly which has a headsurface for facing a magnetic medium, comprising the steps of: forming aread head that includes a magnetoresistive sensor; a making of themagnetoresistive sensor including the steps of: forming an antiparallel(AP) pinned layer structure; forming a ferromagnetic free layer with amagnetic moment that is free to rotate in response to a field signal;and forming a nonmagnetic electrically conductive spacer layer betweenthe free layer and the AP pinned layer structure; the forming of theantiparallel (AP) pinned layer structure including the steps of: formingferromagnetic first and second antiparallel (AP) pinned layers; formingan antiparallel (AP) coupling layer between and interfacing the firstand second AP pinned layers; and the first and second AP pinned layersbeing further formed to self pin one another without assistance of apinning layer; the free layer being further formed with first and secondwing portions that extend in first and second lateral directions beyonda track width of the sensor; forming first and second antiferromagnetic(AFM) layers exchange coupled to said first and second wing portions forlongitudinally biasing the magnetic moment of the free layer parallel tothe head surface and parallel to major planes of the read head; formingthe magnetoresistive sensor with a central portion that extends betweensaid first and second AFM layers; forming first and second lead layersoverlaying the first and second AFM layers respectively and furtheroverlaying first and second portions respectively of said centralportion so that a distance between the first and second lead layersdefines a track width that is less than a distance between the first andsecond AFM layers; forming a cap layer structure that has a fullthickness portion and first and second reduced thickness portions withthe full thickness portion located between the first and second reducedthickness portions; and forming said first and second lead layersengaging the cap layer structure within said first and second reducedthickness portions.
 18. A method of making a magnetic head assemblywhich has a head surface for facing a magnetic medium, comprising thesteps of: forming a read head that includes the steps of: formingnonmagnetic electrically nonconductive first and second read gap layerswith a magnetoresistive sensor located therebetween; and formingferromagnetic first and second shield layers with the first and secondread gap layers located therebetween; a making of the magnetoresistivesensor including the steps of: forming an antiparallel (AP) pinned layerstructure; forming a ferromagnetic free layer with a magnetic momentthat is free to rotate in response to a field signal; and forming anonmagnetic electrically conductive spacer layer between the free layerand the AP pinned layer structure; the forming of the antiparallel (AP)pinned layer structure including the steps of: forming ferromagneticfirst and second antiparallel (AP) pinned layers; forming anantiparallel (AP) coupling layer between and interfacing the first andsecond AP pinned layers; and the first and second AP pinned layers beingfurther formed to self pin one another without assistance of a pinninglayer; the free layer being further formed with first and second wingportions that extend in first and second lateral directions beyond atrack width of the sensor; forming first and second antiferromagnetic(AFM) layers exchange coupled to said first and second wing portions forlongitudinally biasing the magnetic moment of the free layer parallel tothe head surface and parallel to major planes of the read head; andforming the magnetoresistive sensor with a central portion that extendsbetween said first and second AFM layers; forming first and second leadlayers overlaying the first and second AFM layers respectively andfurther overlaying first and second portions respectively of saidcentral portion so that a distance between the first and second leadlayers defines a track width that is less than a distance between thefirst and second AFM layers; forming a cap layer structure that has afull thickness portion and first and second reduced thickness portionswith the full thickness portion located between first and second reducedthickness portions; and forming said first and second lead layersengaging the cap layer structure within said first and second reducedthickness portions; making a write head including the steps of: formingferromagnetic first and second pole piece layers in pole tip, yoke andback gap regions wherein the yoke region is located between the pole tipand back gap regions; forming a nonmagnetic electrically nonconductivewrite gap layer between the first and second pole piece layers in thepole tip region; forming an insulation stack with at least one coillayer embedded therein between the first and second pole piece layers inthe yoke region; and connecting the first and second pole piece layersat said back gap region.